One known apparatus for detection of fire in a building comprises a duct for at least one cable, particularly an electrical cable, through a wall opening in one of the walls of the building. The cable duct has two sealing members sealing the wall opening on opposite sides of the wall. They seal against the cable on the one hand and the wall surface of the passage or pass-through on the other hand and form a fire retardant seal, through which the cable can pass between different fire zones separated from each other by the wall of the building and which isolates these fire zones from each other with respect to the possible spread of a fire.
Cable pass-through or ducts which retard the spread of a fire have already been disclosed, for example in German Patent documents Nos. 34 19 352 and 34 25 429. These ducts are either completely or partly embedded in the wall during its manufacture. Particularly it is possible to mount the duct between the walls of a form for a concrete wall so that it is sealed flush with the wall surfaces in the freshly made wall after removal of the form.
Furthermore apparatus for detection of fire in buildings is known in different forms. It is most common to provide temperature, smoke and/or gas detectors or the like at suitable positions in the spaces to be watched which supply electrical signals which are fed by connecting conductors to a detection device.
Besides emitting of the usual alarm signals by such apparatus, automatic mechanisms and/or devices for fire fighting, particularly sprinkler systems or the like can be activated and can be controlled as may be necessary.
The installation of the fire detection mechanisms occurs as soon as possible after the positioning of the wall framework and is associated with a considerable mounting expense. It is also disadvantageous that the connecting conductors between the sensors and the detection device run either only on an outside of the wall or under plaster, and thus can be relatively readily exposed to the action of a fire and are very sensitive to damage due to fire. This is also true for the sensors.